Energy-dispersive imaging spectroscopy of X-ray emission from the Earth’s aurorae promises to further knowledge in the field of aeronomy. Time- and spatially-resolved observations of fluorescence from the dominant atmospheric components require the detection of X-rays as soft as 390 eV with a resolution of no more than 100 eV at these energies. The Auroral X-ray Imaging Spectrometer (AXIS) instrument of the Disturbed and quiet time Ionosphere-thermosphere System at High Altitudes (DISHA) mission is expected to perform these observations.

The baseline instrument design has suggested the use of an electron-multiplying charge-coupled device (EMCCD). The EMCCD’s electron-multiplying register can reduce the effective readout noise and enable the detection of signals as small as a single photoelectron. For the detection of soft X-rays, however, the noise penalty from the EM register’s stochastic process degrades energy resolution.